Acceleration sensitive shock absorber valve

ABSTRACT

The invention disclosed is a pressurized air-oil, telescopically configured, shock absorber of the type that may be incorporated in an aircraft landing gear or other devices subject to high structural stresses caused by high impact loadings. It consists of a substantially conventional shock absorber modified to include a control valve assembly which programs the opening and closing of the piston position controlling metering orifice thereof by means of a unique valve sleeve normally spring-urged toward a closed metering orifice condition but positioned to effect the opening thereof in proportion with the magnitude of the acceleration to which it is exposed during the impact loading of the aforesaid landing gear or other devices.

[54] ACCELERATION SENSITIVE SHOCK ABSORBER VALVE both of Arlington, Tex.

[73] The United States of Assignee:

Inventors: Jack C. Brady; Kenneth J. Fewel,

America as represented by the Secretary of the Navy Filed: July 2, 1971Appl. No.: 159,319

U.S. C1. ..188/275, 188/282, 188/289,

Int. Cl. ..Fl6f 9/24, Fl6f 9/342 Field of Search ..188/275, 280, 282,284, 286,

[56] References Cited UNITED STATES PATENTS Avner FORElGN PATENTS ORAPPLlCATlONS Primary Examiner-George E. A. Halvosa Attorney-Richard S.Sciascia etal.

[57] ABSTRACT The invention disclosed is a pressurized air-oil, tele-'scopically configured, shock absorber of the type that may beincorporated in an aircraft landing gear or other devices subject tohigh structural stresses caused by high impact loadings. It consists ofa substantially conventional shock absorber modified to include acontrol valve assembly which programs the opening and closing of thepiston position controlling metering orifice thereof by means of aunique valve sleeve normally spring-urged toward a closed meteringorifice condition but positioned to effect the opening thereof inproportion with the magnitude of the acceleration to which it is exposedduring the impact loading of the aforesaid landing gear or otherdevices.

16 Claims, 5 Drawing Figures PATENTEIIHBT I I912 3.6 96, 894

SHEET 2 [1F 2 I I 0 UTILIZATION FIG 4 APPARATUS (AIRPLANE) I AIRFRAMEIII I HINGE JOINT II2 ll5 swoon HINGE ABSORBER JOINT HINGE JOINT ELASTICH4 SUSPENSION SYSTEM f UTILIZATION APPARATUS 4 (AIRPLANE) (LANDmG PWHEELS GEAR gr |l8 CARRIER DECK IMPACT FORCES JACK c. BRADY KENNE'TH J.FEWEL INVENTORS ATTORNEY I I I I I I I I I I I I I I I I ACCELERATIONSENSITIVE SHOCK ABSORBER VALVE STATEMENT OF GOVERNMENT INTEREST Theinvention described herein may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

FIELD OF INVENTION The present invention relates generally to shock.absorbers and, in particular, pertains to an air-oil shock absorber forrelieving the impact .loading of a landing gear of an aircraft, as itrolls over bumps in rough field landings, or as it rolls over arrestingcables on aircraft carrier decks during high-sink speed landingsthereon. ln even greater particularity, the subject invention is animpact alleviator that incorporates an acceleration sensitive valvemechanism, which when mounted in an airoil type shock absorber that isattached between a large inertial mass and a relatively small inertialmass, will allow the latter to oscillate rapidly while under theinfluence of high accelerations without the attendant high impulseloading of the former.

DESCRIPTION OF THE PRIOR ART Heretofore, shock absorbers have beenconstructed in many ways; in fact, too many ways to make a detaileddiscussion thereof meaningful here. Therefore, it should suffice to saythat many thereof have a dashpot-like dampening mechanism therein whichpermits relative telescopic movement between a piston and cylinder tooccur in a controlled manner, so that when certain forces are applied tothe opposite ends thereof, the desired movements therebetween areeffected with a slowed, cushioning action. Of course, the dashpotlikemechanisms incorporated therein are usually of the restricted compressedair or liquid flow varieties, or some combination of both.

For many practical purposes, the shock absorbers of the prior art arequite satisfactory; however, in some instances, and particularly wherethe respective masses interconnected thereby are very large and verysmall thus having relatively large and small moments of inertia theyleave a great deal to be desired. Furthermore, the actions thereofordinarily cannot be controlled sufficiently by the masses attachedthereto alone to provide optimum relative cushioning and, at the sametime, produce the optimum displacements therebetween that are requiredfor numerous operational situations, especially with respect to highlanding speeds and large heavy aircrafts.

SUMMARY OF THE INVENTION The present invention overcomes many of thedisadvantages of the prior art shock absorbers, in that it is or may beconstructed in such manner as to control the shock loadings of a largevariety of relatively large and small cooperating devices, duringnumerous different operational conditions.

Perhaps at the outset, it should be understood that the subjectinvention has general utility for controlling the motion of elasticsuspension systems and, thus, may be designed to be used wherever shockabsorbers are used. On the other hand, the preferred embodimentdisclosed herein is of the type that may be incorporated to an advantagein the landing gear of an aircraft, inasmuch as it was originallyinvented for such purpose. Of course, disclosing it as such will allowthe discussion thereof to be kept as simple as possible. Therefore, itshould readily be appreciated that it would only be necessary to includedesign changes in the subject invention to make it useful in combinationwith any given associated devices, in any appropriate operationalenvironment, or for any circumstances requiring predetermined shockabsorbing functions. Obviously, the making of such designs or designchanges for any given purpose would be well within the purview of theartisan having the benefit of the teachings presented herewith. Hence,without any limitation intended, the

description of the invention may be summarized briefly as being a shockabsorber for alleviating shock loading of effectively interconnecteddevices, wherein one thereof is subjected to a severe impact type offorce while it is desired that the other thereof maintain a ratherstable condition as a result of said shock load being graduallytransferred thereto rather than being suddenly transferred thereto.

In general, it may be said that this invention incorporates therelatively moving piston and cylinder arrangement, as is alreadyconventional in the art. Said piston and cylinder are, of course,respectively designed to connect in a suitable manner to the two deviceswhich are intended to be relatively shock cushioned. It is of thecontrolled or programmed airoil-orifice dashpot type, too; but thestructural configurations of the elements effecting such arrangement areunique and constitute a new combination of elements when combined withthe aforesaid well known pressurized air-hydraulic pressurized pistonand cylinder arrangement, and will cause vastly improved results to beproduced. For example, by employing properly designed spring loadedcontrol weights, the size of dashpot orifices may be regulated tocontrol the flow of dampening oil therethrough in accordance with theseverity of the impact being encountered by one or both of the deviceseffectively interconnected by means of the instant shock absorber. As aresult, the oscillatory shock transfers that occur between such devicessuch as, for instance, those that occur between the fuselage and wheelsof an aircraft during landing are controlled in such manner as toprovide optimum protection for both thereof because the subjectinvention is acceleration sensitive and responsive.

It is, therefore, an object of this invention to provide an improvedshock absorber.

Another object of this invention is to provide a method and means forcontrolling the relative motion occurring and force transferred betweena pair of effectively interconnected devices, as a result of one thereofbeing subjected to an impact that might otherwise disable or adverselyaffect the other.

Still another object of this invention is to provide an improved methodand means for reducing the shock loading of predetermined devices thatotherwise would be subjected to destructive impact forces.

A further object of this invention is to provide an improved aircraftlanding gear shock absorber.

A further object of this invention is to provide an impact shockabsorber that is sensitive to and controlled by accelerations.

Another object of this invention is to provide a method and means forprotecting an aircraft during landing.

Still another object of this invention is to provide a method and meansfor safely transferring kinetic energy from a mass having small inertiato a mass having relatively large inertia when said mass having a smallinertia is subjected to impact forces.

Another object of this invention is to provide an acceleration sensitiveshock control valve mechanism that may be incorporated to an advantagein many otherwise conventional shock absorbers.

Other objects and many of the attendant advantages will be readilyappreciated as the subject invention becomes better understood byreference to the following detailed description, when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a quasi-pictorial view of atypical shock absorber incorporating the subject invention;

FIG. 2 is.an elevational view of a cross sectionof the accelerationsensitive shock absorber valve assembly incorporated in the shock strutof FIG. I, illustrated in its most compressed condition;

FIG. 3 is an elevational view, mostly in cross section,

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIG. 1, there isshown a representative shock absorber 11 of the telescopic variety andof the type that may be incorporated in an aircraft landing gear or anyother mechanism, mechanisms, or systems subject to impact or oscillatoryforces. As may readily be seen, the external appearance and constructionthereof may, if so desired, be conventional, with the exception of theincorporation of the unique valve assembly to be discussed below.Accordingly, shock absorber 11 contains a ring-like attaching member oreye connector 12 having a hole 13 therethrough adapted for receiving abolt or journal (not shown) which is ordinarily attached to one of thecooperating devices between which it is desired to control shockloading.

Connector 12 is integrally attached .to an end tubelike cap 14, theouter extremity of which is closed, and the inner extremity of which isan internally threaded orotherwise capable of being connected to acylinder 15, which likewise may be threaded at the external end thereoffor such purpose. Within cylinder 15 is disposed a slidable piston 16which extends through a conventional packing gland or other seal 17 outthe other end thereof. As such, the aforesaid cylinderpiston arrangementis usually considered to be an elongatable compression type shock strut,especially when it is associated with an aircraft. Attached to the endof piston 16 is a connecting rod 18, and connected thereto is anothereye connector 19, likewise having a hole 20 therethrough adapted forreceiving a bolt or journal (not shown) that is ordinarily connected tothe other of the aforementioned devices between which it is desired tocontrol shock loading.

Located on wall of end cap 14 is a boss 21 with a hole or passagewaytherethrough, and inserted therein is a fitting 22, adapted forattaching a compressed air or other pneumatic tube or hose thereto.Also, located on thewall of cylinder 15 is another boss 23 with a holeor passageway therethrough, and another fitting 24, adapted forattaching an oil or hydraulic fluid line thereto, is inserted therein.

At this time, it should be understood that, with the exception of theinternal structures of the aforesaid telescopically disposed cylinder 15and piston 16, and the hydraulic valve assembly incorporated therein,all of the other parts of shock absorber l 1 are well known andconventional per se. Nevertheless, as previously suggested, when saidconventional parts are combined in the unique manner with saidcylinder-piston-valve assembly aboutto be disclosed, they form a newcombination of elements heretofore unknown which, for many practicalpurposes, produces vastly improved results heretofore not obtainablefrom the prior art.

FIG. 2 depicts only the section of shock absorber 11 which contains theinteracting cylinder-piston-valve assembly mentioned above. Accordingly,said section contains the aforementioned cylinder 15 and piston 16; and,hence, for the sake of clarity and simplicity of disclosure, they willbe identified by the same reference numerals, respectively. In thisfigure, the shock absorber is shown as being in its most compressedcondition, in order to be structurally clear and yet not require moredrawing space then is available.

As may readily be seen in FIG. 2, cylinder 15 contains an inner wall 31,which is preferably shaped in a somewhat conical fashion, the peak orapex of which theoretically extends upwardly at the center thereof.However, at the apex center of wall 31 and extending therethrough is ametering hole or orifice 32, the size of which is varied by a taperedpipe-like metering pin 34 that is slidable therein. Metering pin 34 isintegrally connected to the top of a head portion 35 of piston 16 insuch manner that the hollow 36 thereof constitutes a hydraulic fluidpassageway therethrough. A pipe 37 is also connected to head 35 in suchmanner that the hollow 38 thereof coincides with and thus constitutes anextension of passageway 36. Preferably, the design of cylinder 15,piston 16, metering pin 34, and pipe 37 should be such that the centeror longitudinal axis thereof substantially coincide with thelongitudinal axis of sheet absorber l 1 itself.

As viewed in FIG. 2, the upper end of metering pin 34 is open, and thelower end of pipe 37 closed. However, disposed at predeterminedpositions along'pipe 37 are upper and lower metering orifices 39 and 41,respectively.

Integrally connected to the upper end of cylinder 15 is a housing 42,which, for all practical purposes, could be considered as an extensionof said cylinder. However, its purpose is to provide a chamber which, inturn, acts as a reservoir for compressed air' 43 and for a liquid poolof oil or'hydraulic fluid 44, the level of which during normal operationis such that the upper open end of pipe 34 remains below the surface 45thereof.

In this particular preferred embodiment, head 35 is domed in such mannerthat the upper surface is substantially compatible with the lowersurface of wall 31 and still leaves a high pressure chamber 46 ofpredetermined space or volume therebetween when piston is in itsuppermost position in cylinder 16. Of course, as will be described morefully below, a portion of the aforesaid hydraulic oil 44 is disposed inchamber 46.

Piston head 35 has a plurality of control parts 47 preferably threedisposed at 120 degree intervals therearound extending through it insuch manner that high pressure chamber 46 is always effectivelyconnected to a valve chamber 48 located immediately below head 35 withinpiston 16. The lower closure of said chamber is, of course, a solid wall49.

For the purpose of facilitating the construction of the subjectinvention, piston 16 has been designed to have a removable head-skirtassembly. Hence, the upper end of the skirt of piston 16 containsinternal threads 52, and the outer diameter of head 35 has externalthreads 53 that are complementary therewith. Thus, by merely screwinghead 36 into the top skirt of piston 16, valve chamber 48 is formed.Obviously, such construction allows a control valve assembly 54 to beinstalled and removed expeditiously during manufacture and maintenancethereof.

The principle of construction and operation of valve assembly 54 isexceedingly simple but, yet, profound, because it causes such excellentresults to be effected by the entire shock absorber constituting thisinvention. An inertial sleeve or body or revolution 55, preferably madeof metal having a predetermined mass, has a bearing bore therethroughalong the longitudinal axis thereof. Because body 55 ismounted on andintended to be slidable on pipe 37, the inside diameter thereof shouldbe such as to provide a slip-fit bearing between it and the outsidesurface of pipe 37, while allowing for some of hydraulic fluid 44 toprovide inherent lubrication therefor.

Perhaps it may be noteworthy that body 55 is somewhat top-shaped havinga winged or flanged portion 56, since such geometrical configurationallows easy assembly of the other elements cooperating therewith;however, it should be appreciated that it is not intended that the shapebe limited thereto, inasmuch as it would be obvious to the artisan todesign other workable configurations, as well. Nevertheless, it has aflat upper face 57 which will abut that portion of the lower surface ofhead 35 that immediately surrounds pipe 34. It also contains a pluralityof holes 58 the number of which is identical to the number of theaforementioned lower metering orifices 41 in pipe 37 which are locatedalong the length thereof at such distance from the top, flat end thereofthat, when body 55 has moved downward sufficiently to uncover uppermetering orifices 39, lower metering orifices 41 are uncovered, too.Hence, it may readily be seen that hollow metering pin 34, slidable body55, and orifices 39 and 41 cooperate in a sleeve-valve fashion to timelypermit hydraulic oil to pass from chamber 48, through pipe 37, throughmetering pin 34, and into reservoir 44 in housing 42.

To limit the rotational travel of body mass 55, a hole 59 is locatedtherein which is preferably normal to the longitudinal axis thereof.Within hole 59 is disposed a snugly fit but removable key or guide pin61, which slidably fits in a restrictive groove 62 located in linetherewith in lower pipe 37. Hence, body can move up and down to theextent permitted by the length of groove 62, and when so doing, keepsholes 58 in line with orifices 41 to effect the coincidence thereofduring high acceleration periods. A coil type control spring 63 isdisposed around body 55 between a predetermined surface of the aforesaidflange 56 (the surface of which, of course, is contingent upon thegeometrical configuration thereof) and the surface 64 of a stop flange65 that may either be attached to the end of pipe 37 by any convenientmeans or abut the aforesaid wall 49. Body 55, on the one hand, must belong enough to simultaneously cover the aforesaid upper and lowermetering orifices 39 and 41 when it is in its abutment position with theunderside of head 35; on the other hand, it must be short enough toallow it to slide on pipe 37 to simultaneously uncover said upper andlower metering orifices 39 and 41 before it reaches the limit of itsdownward travel.

The external surface configuration of the housing portion of piston 16,which extends down into the lower portion of cylinder 15, is or may beconventional, in that, effectively, there are several bearing surfaces66 and 67 on the former which are slidable on the inside surface of thelatter. Of course, there is a snug fit and a seal ring 71 therebetweento prevent the excessive bypassing of hydraulic oil therebetween butstill provide some lubrication thereat.

As is conventional in telescopic air-oil shock absorbers for hydraulicfluid control purposes during normal operation, a chamber 68(surrounding piston 16) is provided. Because it is normally adjacent tofiller hydraulic fitting 24, it is thus filled with hydraulic fluidwhich, in turn, flows through the conventional flow check means 69 insuch quantities as to provide suitable pressure release between chamber46 and 68 as would be required for normal support during non-impactconditions.

It should perhaps be noteworthy that the telescopic construction ofthose parts of the subject shock absorber not directly or indirectlyinteracting with the aforesaid valve assembly 54 may be so designed aswill facilitate its being used as a shock absorber for any particulardevice, including any particular aircraft. Obviously, it would be wellwithin the purview of one skilled in the art having the benefit of theteachings presented herewith to make the necessary design choices toconstruct a shock absorber for any desired use. Therefore, the specificstructural configurations illustrated in FIG. 1 and 2 should not beconsidered to be limiting but, instead, merely representative of typeswhich may be employed to an average wherever it is desired to cushion ordampen impact forces.

Referring now to FIG. 3, there is shown another preferred embodiment ofthe subject invention. From a structural standpoint, it is similar tothe shock absorber illustrated in FIG. 2, with the exception of thoseparts pertaining to the acceleration sensitive control valve portionthereof. Hence, for the sake of simplicity of disclosure, only saidcontrol valve portion will be described, and in so doing, the referencenumerals used in FIG. 1 will be used for like parts, insofar as it isexpedient to do so, and only as needed for clarity.

As may readily be seen, the shock absorber of FIG. 3 is depicted inintermediately elongated condition ratherthan in a completely compressedcondition, as depicted in FIG. 2 in order to disclose the relativedisposition of the various and sundry elements from a slightly differentperspective.

Due to the aforesaid elongation, as shown in FIG. 3, piston 16 islocated lower in piston 15 and hydraulic fluid 44 fills high pressurechamber 46, which is now of considerably larger volume. Fluid 44 alsofills ports 47 and that portion of piston chamber 54 not occupied by thecontrol valve assembly discussed now in some detail.

To the underside of piston head 35, a hollow pipe 81 is connected insuch manner as to extend down into chamber 54. Disposed through thewall. thereof at predetermined distances along the length thereof is aplurality of upper and lower metering orifices 82 and 83, respectively.And located for slidable movement within the hollow of pipe 81 is asleeve 84, which during normal operation, abuts the underside of head35. A plurality of slots or holes 85 and 86 are located in the wall ofsleeve 84 at such positions that they respectively coincide withmetering orifices 82 and 83, when sleeve 84 moves out of abutment withthe underside of piston head 35, but allows said orifices 82 and 83 toremain closed during normal, non-impact shock absorber operation.

Near the end of pipe 81 opposite the end thereof connected to head 35 isa plurality of external threads 87 and a bearing surface 88. An end cap89 having internal threads: 91 (that are complementary with theaforesaid external threads 87) is screwed on the end of pipe 81. Toinsure a fluid seal between threaded pipe 81 and end cap 89, a groove 92is located around the inside periphery of cap 89, and a suitable O-ring93 is disposed therein. Of course, when cap 89 is-screwed tightly onpipe 81, O-ring 93 is pressed against bearing surface 88 withsufficientforce to provide a hydraulic seal thereat.

Between the lower end of sleeve 84 and the upper inside surface of endcap 89, a resilient means, such as a coil spring 94, is disposed in suchmanner as to urge sleeve 84 toward abutment with the underside of head35, and thereby cause metering orifices 82 and 83 to be closed at thattime.

Located in the lower end of pipe 81 (as viewed in FIG. 3) is a pair ofdiametrically opposed, longitudinally disposed guide grooves 96 and 97.And attached to the end of sleeve 84 as by press fit or otherappropriate attachment means.- is a keeper pin 98 of such length that itwill extend into and slide longitudinally within the guide grooves 96and 97, thereby preventing rotation of sleeve 84 whenever sleeve 84moves up and down within pipe 81, due to the forces of accelerationbeing applied thereto. Obviously, inasmuch as keeper pin 98 cannotrotate, and since it is connected to sleeve 84, sleeve 84 cannot rotateeither; hence, slots 85- and 86 will always be positioned in such placesas will allow them to coincide with and thus open metering orifices 82and 83 whenever sleeve 84 moves out of abutment with the underside ofpiston head 35, so as to timely allow passage of the hydraulic fluidfrom chamber 46, through ports 47, through orifices 82 and 83, throughslots 85 and 86",through the hollow of sleeve 84 and bore 36 or meteringpin 34, and back into the hydraulic reservoir of cylinder housing 42above wall 31.

As previously indicated, FIG. 4 illustrates a very generalized buttypical version of a system that could incorporate the subject inventionto an advantage. lt is portrayed herewith toinsure that it is understoodthat the invention has broad utility, although it is particularly usefulin aircraft landing gears, as well.

For example, a utilization apparatus 1 10 (such asan airplane airframe)may be physically connected through a suitable hinge joint 1 1 1 to oneend of a shock absorber 112 of the, type of this invention, with theother end thereof likewise physically connected through a suitable hingejoint 1 13 to another utilization apparatus 114 (such as, for instance,airplane wheels). In addition, still another hinge joint 115 may bephysically connected to hinge joints 111 and 113, and it is shown inthis particular manner merely to disclose that the physical structurethereof should be such as will allow straight line, telescopic motion tooccur within shock absorber 112. Obviously, other structuralconfigurations would suffice for such purpose, as well; hence, thepossible applications of the invention are practically unlimited.

Of course the aforementioned elements 111 through 115 constitute arepresentative elastic suspension system 116 (such as, perhaps, anaircraft landing gear).

As shown in FIG. 4, a carrier deck 117 may supply impact forces 118 toutilization apparatus 114, in the event such apparatus happens to be thewheels of an airplane landing thereon. It is shown in this manner forthe purpose of providing clarity for one specific application of theinvention, although it would be obvious to. the artisan that sucharrangement could be useful in other applications, too.

FIG. 5 graphically illustrates the several loads encountered by shockstruts in an aircraft landing gear as a result of impact thereof onaircraft carrier deck with and without arresting cables during high sinklandings under different operational conditions. Although 'differentloads will occur for different sizes, weights, and landing speeds ofaircraft, the curves of FIG. 3 may be considered as being typical forcomparative purposes.

Solid line curve 121 indicates the shock strut loading encountered by anaircraft landing on an aircraft carrier deck without arresting cableimpact and without the subject alleviator or shock absorber beingincorporated in the landing gear thereof.

Short dashed line 122 indicates the shock strut loading encountered bythe same aircraft landing on a carrier deck with arresting cable impactbut without the subject invention being incorporated in the landing gearthereof.

Dash-dot line curve 123 indicates the shock strut loading encountered bythe same aircraft landing on a carrier deck with arresting cable impactbut without the subject invention being incorporated in the landing gearthereof.

Obviously, the aforementioned curves are all plotted on a single graphhaving load in pounds as the ordinate thereof and time in seconds as theabscissa thereof, in order to facilitate the making of comparisons ofthe various loads encountered as a result of the occurrence of severaldifferent operational and structural combinations. They, incidentally,will be explained more fully during the discussion of the operation ofthe invention presented below.

MODE OF OPERATION The operation of the subject invention will nowbediscussed briefly in conjunction with all of the figures of the drawing.

Because the device constituting this invention may have any geometricalconfiguration that will give it such physical characteristics as willallow it to be included as a part of any aircraft landing gear or, forthat matter, as a part of any elastic suspension system in which themotion of the relatively moving members thereof is preferably controlledfor restoration of equilibrium or other dampening purposes the externalappearance and the design of the internal structure of the shockabsorbers of FIG. I may be whatever will provide optimum operationtherefor. Thus, it should be understood that FIG. 1 is merely exemplaryand that it is only disclosed to show one preferred embodiment of theinvention.

In the telescopic version of the shock absorber 11 of FIG. 1, eyes 12and 19 are connected to the relatively moving parts that are to beshocked cushioned, respectively. Because the various and sundryapplications of shock absorber 11 are too numerous to depict in thedrawing or mentioned in this specification, they have not been disclosedspecifically, other than to indicate that there are many thereof. So,for the purpose of keeping this case as simple as possible, it will beconsidered that shock absorber 11 is incorporated in a properconventional manner. in the landing gear (not shown) of an aircraft inwhich the sprung weight thereof exceeds the unsprung weight thereof and,consequently, any oscillatory vibration or excessive impact loadingproblems that would ordinarily exist therebetween during the landing ofsaid aircraft is alleviated to a considerable extent by the invention.

As is well known in the aircraft art, when an aircraft lands on a runwayor other surface be it at an airport, in a rough field, or on anaircraft carrier deck considerable stress occurs within the entirestructure of the landing gear and, unfortunately, some of it istransmitted to the frame or fuselage of the craft. However, it has longbeen determined that the use of landing gear type of pressure reliefmechanisms between the aircraft wheels and the air frame considerablyreduce the stresses in both thereof, especially during high impactlandings of large, heavy airplanes. Moreover, it is also well known andconventional to use shock absorbers in conjunction with landing gearpressure relief mechanisms, and that the proper control thereof providesan additional reduction in the aforesaid stresses, thereby increasingthe life, efficiency, and safety of landing gears and landing gear airframe combinations. This is true with respect to ordinary airplaneslanding on conventional airport runways; however, it is even moreevident during landings on rough terrain or on tossing aircraft carrierdecks which contain arresting cables for stopping airplanes as soon aspossible after they touch down. With such exemplarily settings in mind,the specific operational characteristics of the subject shock absorberwill now be discussed in detail.

Being an acceleration sensitive device, the subject shock absorber willfunction normally until it is exposed to the shock load of a bump,whereupon piston 16 is moved rapidly enough within cylinder 15 by aforcing acceleration to cause the inventive portion of the subject shockabsorber to become operative. When said forcing acceleration is ofsufficient magnitude to cause the unseating of controlmass 55, it will,relatively speaking, move downwardly (as viewed in FIG. 2) along pipe37, thereby compressing spring 63 and subsequently opening upper andlower metering orifices 39 and 41. At that time, that portion ofhydraulic'oil 44 contained within high pressure chamber 46 is .portedthrough chamber ports 47, through metering orifices 39 and 41, upthrough the hollow or relief passage of metering pin 34, into compressedair chamber 46 and back into reservoir pool 44. Such fluid flow, ofcourse, allows a controlled pressure release to occur within highpressure chamber 46, which, in turn, allows the piston 16 to be movedand compressed further into cylinder 15, in accordance with the amountof acceleration to which body was exposed during impact, therebycushioning the forces of said impact as far as the device connected tocylinder 15 is concerned. After the bump has been traversed, controlspring 63 will cause body mass 55 to be seated against the lower surfaceof wall 35, closing metering orifices 39 and 41, after which the entireshock absorber will otherwise function in a normal fashion again.

The proper design of the mass of body 55, the size of orifices 39 and41, and the viscosity of the hydraulic oil 44 will, of course, cause theoperation of the shock absorber to be optimized for any given size shockabsorbers and any given operational circumstances.

One of the more important advantages of this type of device lies in thefact that the sprung air frame mass of an airplane invariably has aninertia that is large compared to the inertia of the unsprung portion ofthe landing gear; therefore, the subject invention allows the unsprunglanding gear mass to pulse quickly when under the influence of highaccelerations resulting from high impact forces. This, in turn, allowsrapid oscillation of the unsprung landing gear mass without attendantdeleterious high impulse loading of the air frame of the airplane tooccur, which would otherwise adversely affect the dynamic stability andperhaps pilot control thereof.

The operation of the embodiment of FIG. 3 is very similar to that of theembodiment of FIG. 2. Therefore,

it will be discussed very briefly, with emphasis only on theacceleration sensitive valve assembly.

When an impact force is applied to the bottom of piston 16 (as viewed inFIG. 3), sleeve 84, due to its inertia, tends to remain stationary and,thus, relatively speaking, slides downward within pipe 81 to causeorifices 82 and 83 to be opened by slots 85 and 86, respectively. As aresult, the high pressure hydraulic fluid rapidly flows therethroughinto the hollow of sleeve 84, up through bore 36 in piston head 35 andmetering pin 34 and into the compressed air-hydraulic fluid reservoirabove wall 31 in cylinder housing 42. Such rapid flow, in turn,effectively reduces the pressure in chamber 46 between the top of pistonhead 35 and the bottom of wall 31, to thereby permit the rapid butcushioned movement of piston 16 further into cylinder 15. Of course, aseries of such impact forces may occur, and, hence, piston 16 is forcedto move up and down within cylinder 15. And each time it does,acceleration sensitive sleeve 84 functions as indicated above.

Referring now to FIG. 5, there is shown a load-time diagram which wascalculated for a main gear strut of the type shown in FIG. 3; however,by analogy, it is pertinent to the operation of the species of FIG. 2,too, because the inventive concepts existing therein are substantiallyidentical to those of the device of FIG. 3, even though the respectivestructures thereof are somewhat different.

As may readily be seen from the exemplary curves of FIG. 5, the variousand sundry cushioning effects encountered vary according to prevailinglanding conditions and whether or not the shock strut constituting theinstant invention is included in the landing gear of the airplane. Forexample, curve 121 shows shock strut load vs. time for the situationwhere an aircraft is landed on a carrier deck with-the subject shockabsorber omitted from its landing gear and with the wheels encounteringno restraining cable. Although, shock oscillation occurs, it is not toogreat, and thus the strain on the landing gear may not be excessive. Insuch case, the oscillations shown are attributable to the naturalfrequency of oscillation of the landing gear-aircraft system in reactionto the initial transducer impact. However, when a restraining cable isused and encountered by the wheels of the landing aircraft withoutbenefit of the subject alleviator, curve 122 shows that the shock strutload vs. time is quite large (relative to the aforementioned condition)and, thus, the strain on the landing gear could be so great as to causeimpairment thereof and perhaps cause the air frame of the airplane tocrash into the carrier deck probably to the detriment of the pilot andcargo, as well as causing damage to the airplane and the carrier deck.Accordingly, it may readily be seen that-if improvement is desired, asuitable shock absorber must be incorporated in the airplanes landinggear.

When the subject shock absorber, is incorporated in the landing gear,the shock strut load vs. time which occurs when an arresting cable isencountered is depicted in curve 123. j

The oscillations of curves 122 and 123 are attributable to the touchdownimpact and the briefly subsequent cable impact.

Although the loading force of curve 123 is oscillatory and greater thanit would be without an impact cable, it is considerably less than thesituation of arresting cable and no shock absorbers. Therefore, for thisparticular purpose which should only be considered as exemplary thesubject invention vastly improves the shock loading characteristics of ahigh mass airplane fuselage when it is combined with a relatively lowmass landing gear, thereby increasing the life, safety, versatility,etc., of all concerned.

As implied by the system of FIG. 4, substantially comparable performancewill occur in even a generalized system, regardless of the respectivegeometrical configurations.

As implied by the general structural configuration of the system of FIG.4, the performance thereof is substantially comparable to theperformance discussed above in conjunction with the devices of FIGS. 1,2,

and 3, and possible associated equipment. Therefore, the load-timecurves of FIG. 5, byanalogy, are applicable thereto also, althoughobviously a different family of such curves would be obtained fordifferent relative masses of utilizationapparatus 1 10 and 1 14.

In view of the foregoing, it may readily be seen that the unique shockabsorber constituting this invention produces results heretoforeunobtainable from the prior art devices, and especially from those priorart devices which are intended to control the loading and motion oflarge inertia apparatus such as, for example, the large, heavy fuselagesof airplanes and relatively small inertia devices such as, for example,the unsprung smaller and lighter weight portions of the landing gears ofsaid airplanes.

Obviously, other embodiments and modifications of the subject inventionwill readily come to the mind of.

one skilled in the art having the benefit of the teachings presented inthe foregoing description and the drawings. It is, therefore, to beunderstood that this invention is not to be limited thereto and thatsaid modifications and embodiments are intended to be included withinthe scope of the appended claims.

What is claimed is:

1. In a pressurized air-hydraulic shock absorber, the

combination comprising:

cylinder means, having a closed end and an open end;

means attached'to said cylinder means for the connection thereof to afirst predetermined utilization apparatus;

a first wall located a predetermined intermediate position along thelength of said cylinder means in such manner as to form a cylindricalchamber between it and the aforesaid closed end thereof;

a metering orifice located in the center of said first wall;

piston means, having a head and a housing extending therefrom,telescopically mounted for slidablev disposition within said cylindermeans;

a plurality of ports disposed through the head of said piston means;

a second wall located within the housing of said piston means in suchmanner as to form a piston chamber between it and the head thereof;

a metering pin means, having an elongated barrel which is configured insuch predetermined manner as to have a first outside diameter at one endthereof that provides a slip-fit with the inside diameter of theaforesaid metering orifice when located therein and a predeterminedsecond diameter at the other end thereof that is smaller than said firstoutside diameter, connected to one side of the head of said piston meansin such manner that the smaller diameter end thereof extends throughsaid metering orifice and a predetermined distance into said cylindricalchamber;

a continuous bore extending through the head of said piston and theentire length of said metering pin means;

a hollow pipe means, one end of which is connected to the other side ofthe head of said piston means in such manner as to cause it to extend apredetermined distance into said piston chamber and effect a continuouspassageway between the hollow thereof and the aforesaid bore;

means connected to the other end of said hollow pipe means for effectingthe closure thereof;

passage means extending through the wall of said hollow pipe means;

control means, having a mass that is responsive to predeterminedaccelerations, slidably mounted in contiguous disposition with saidhollow pipe means in suchmanner that it is movable into and out ofabutment with the head of said piston means and will close and variableopen the aforesaid passage means when so positioned, respectively;

means, having a predetermined compression rate, ef-

fectively mounted between the end closure means of said hollow pipemeans and said control means for resiliently urging said control meanstoward the position of abutment with the head of saidv piston means andthereby effect closure of the aforesaid passage means;

hydraulic fluid means disposed so as to partially fill said cylindricalchamber to a predetermined level and completely fill said pistonchamber, the ports extending through the head of said piston means, andthe space between the head of said piston means and the aforesaid firstwall of said cylinder means;

means connected to said cylinder means and disposed in slidable contactwith the external surface of the housing of said piston means foreffecting a hydraulic fluid seal therebetween when said piston means istelescopically disposed therein; and

means connected to said piston means for the connection thereof to asecond predetermined utilization apparatus.

2. The device of claim 1, wherein said means connected to the other endof said hollow pipe means for effecting the closure thereof comprises asolid wall integrally attached thereto.

3. The device of claim 1, wherein said means connected to the other endof said hollow pipe means for effecting the closure thereofcomprises:

a solid wall; and

an end flange connected to said solid wall in such manner as to providea stop means for that end of the aforesaid resiliently urging meanswhich is opposite said control means.

4. The device of claim 1, wherein said control means, having a mass thatis responsive to predetermined accelerations, slidably mounted incontiguous disposition with said hollow pipe means in such manner thatit is movable into and out of abutment with the head of said pistonmeans and will close and variably open the aforesaid passage means whenso positioned, respectively, comprises:

a body of revolution, having a longitudinal axis and a hole extendingthrough said body of revolution along the longitudinal axis thereof,slidably mounted on the outside of said hollow pipe means;

a face located at one end of said body of revolution and disposed normalto the longitudinal axis thereof adapted for abutment with the head ofsaid piston means; and

flange means connected to said body of revolution in such manner as toextend therefrom in a plane that is substantially perpendicular to thelongitudinal axis thereof.

5. The device of claim 1, wherein said control means, having a mass thatis responsive to predetermined accelerations, slidably mounted incontiguous disposition with said hollow pipe means in such manner thatit is movable into and out of abutment with the head of said pistonmeans and will close and variably open the aforesaid passage means whenso positioned, respectively, comprises:

a hollow sleeve slidably mounted within said hollow pipe means forabutment of one end thereof with the head of said piston means; and

aperture means located through the wall of said hollow sleeve at suchposition along the length thereof that it coincides with the passagemeans of said hollow pipe means as said sleeve moves out of abutmentwith the head of said piston means.

6. The device of claim 1, wherein said means, having a predeterminedcompression rate, effectively mounted between the end closure means ofsaid hollow pipe means and said control means for resiliently urgingsaid control means toward the position of abutment with the head of saidpiston means and thereby effect closure of the aforesaid passage meanscomprises a coil spring.

7. The device of claim 1, wherein said means, having a predeterminedcompression rate, effectively mounted between the end closure means ofsaid hollow pipe means and said control means for resiliently urgingsaid control means toward the position of abutment with the head of saidpiston means and-thereby effect closure of the aforesaid passage meanscomprises:

a coil spring; and

means connected to the end closure means of said hollow pipe means foreffectively restraining the movement of that end of said coil springwhich is opposite said control means.

8. The device of claim 1, wherein said hydraulic fluid means disposed soas to partially fill said cylindrical chamber to a predetermined leveland completely fill said piston chamber, the ports extending through thehead of said piston means, and the space between the head of said pistonmeans and the aforesaid first wall of said cylinder means comprises aliquid having a predetermined viscosity.

9. The device of claim 1, wherein said means connected to said. cylindermeans and disposed in slidable contact with the external surface of thehousing of said piston means for effecting a hydraulic seal therebetweenwhen said piston means is telescopically disposed therein comprises apacking gland.

10. The invention of claim 1 further characterized by a pair of fittingsattached to said cylinder means in such manner as to provide means forsupplying compressed air and hydraulic fluid thereto, respectively.

11. The device of claim 1, wherein said means connected to the other endof said hollow pipe means for effecting the closure thereof comprises:

a plurality of threads located around the outside of that end of saidhollow pipe means to be closed; and

a cap, having internal threads that are compatible with the aforesaidplurality of threads, screwed on the end of said hollow pipe means.

12. The invention of claim 11, further characterized by means disposedbetween said hollow pipe means and said cap for effecting a fluid sealtherebetween.

13. The invention of claim 1, further characterized by means connectedbetween said hollow pipe means and said control means for limiting therotation of said control means a predetermined amount with respect tosaid hollow pipe means.

14. The device of claim 13, wherein said means connected between saidhollow pipe means and said control means for limiting the rotation ofsaid control means a predetermined amount with respect to said hollowpipe means comprises:

a hole'located in said control means which extends therethrough in suchmanner as to provide an open passageway to the external surface of saidhollow pipe means;

a groove located in the outer surface of said hollow pipe means, saidgroove being elongated in the direction of travel of said control means,and located in contiguous disposition with the aforesaid hole for theentire length thereof; and

a pin removably press fitted within said hole in such manner as to causethe inner end thereof to slidably fit in said groove and be travellimited thereby. 1

15. The device of claim 13, wherein said means connected between saidhollow pipe means and said control means for limiting the rotation ofsaid control means a predetermined amount with respect to said hollowpipe means comprises:

at least one groove, elongated in the direction of travel of saidcontrol means, located in the inner surface of said hollow pipe means;and

means connected to said control means extending into said groove in suchmanner as to provide a slidable fit and a rotational limitationtherebetween.

16. The device of claim 15, wherein said means connected to said controlmeans and extending into said groove in such manner as to provide aslidable fit and a rotational limitation therebetween comprises a keeperpin.

1. In a pressurized air-hydraulic shock absorber, the combination comprising: cylinder means, having a closed end and an open end; means attached to said cylinder means for the connection thereof to a first predetermined utilization apparatus; a first wall located a predetermined intermediate position along the length of said cylinder means in such manner as to form a cylindrical chamber between it and the aforesaid closed end thereof; a metering orifice located in the center of said first wall; piston means, having a head and a housing extending therefrom, telescopically mounted for slidable disposition within said cylinder means; a plurality of ports disposed through the head of said piston means; a second wall located within the housing of saiD piston means in such manner as to form a piston chamber between it and the head thereof; a metering pin means, having an elongated barrel which is configured in such predetermined manner as to have a first outside diameter at one end thereof that provides a slip-fit with the inside diameter of the aforesaid metering orifice when located therein and a predetermined second diameter at the other end thereof that is smaller than said first outside diameter, connected to one side of the head of said piston means in such manner that the smaller diameter end thereof extends through said metering orifice and a predetermined distance into said cylindrical chamber; a continuous bore extending through the head of said piston and the entire length of said metering pin means; a hollow pipe means, one end of which is connected to the other side of the head of said piston means in such manner as to cause it to extend a predetermined distance into said piston chamber and effect a continuous passageway between the hollow thereof and the aforesaid bore; means connected to the other end of said hollow pipe means for effecting the closure thereof; passage means extending through the wall of said hollow pipe means; control means, having a mass that is responsive to predetermined accelerations, slidably mounted in contiguous disposition with said hollow pipe means in such manner that it is movable into and out of abutment with the head of said piston means and will close and variable open the aforesaid passage means when so positioned, respectively; means, having a predetermined compression rate, effectively mounted between the end closure means of said hollow pipe means and said control means for resiliently urging said control means toward the position of abutment with the head of said piston means and thereby effect closure of the aforesaid passage means; hydraulic fluid means disposed so as to partially fill said cylindrical chamber to a predetermined level and completely fill said piston chamber, the ports extending through the head of said piston means, and the space between the head of said piston means and the aforesaid first wall of said cylinder means; means connected to said cylinder means and disposed in slidable contact with the external surface of the housing of said piston means for effecting a hydraulic fluid seal therebetween when said piston means is telescopically disposed therein; and means connected to said piston means for the connection thereof to a second predetermined utilization apparatus.
 2. The device of claim 1, wherein said means connected to the other end of said hollow pipe means for effecting the closure thereof comprises a solid wall integrally attached thereto.
 3. The device of claim 1, wherein said means connected to the other end of said hollow pipe means for effecting the closure thereof comprises: a solid wall; and an end flange connected to said solid wall in such manner as to provide a stop means for that end of the aforesaid resiliently urging means which is opposite said control means.
 4. The device of claim 1, wherein said control means, having a mass that is responsive to predetermined accelerations, slidably mounted in contiguous disposition with said hollow pipe means in such manner that it is movable into and out of abutment with the head of said piston means and will close and variably open the aforesaid passage means when so positioned, respectively, comprises: a body of revolution, having a longitudinal axis and a hole extending through said body of revolution along the longitudinal axis thereof, slidably mounted on the outside of said hollow pipe means; a face located at one end of said body of revolution and disposed normal to the longitudinal axis thereof adapted for abutment with the head of said piston means; and flange means connected to said body of revolution in such manner as to extend therefrom in a plane that is substantially perpendicular to tHe longitudinal axis thereof.
 5. The device of claim 1, wherein said control means, having a mass that is responsive to predetermined accelerations, slidably mounted in contiguous disposition with said hollow pipe means in such manner that it is movable into and out of abutment with the head of said piston means and will close and variably open the aforesaid passage means when so positioned, respectively, comprises: a hollow sleeve slidably mounted within said hollow pipe means for abutment of one end thereof with the head of said piston means; and aperture means located through the wall of said hollow sleeve at such position along the length thereof that it coincides with the passage means of said hollow pipe means as said sleeve moves out of abutment with the head of said piston means.
 6. The device of claim 1, wherein said means, having a predetermined compression rate, effectively mounted between the end closure means of said hollow pipe means and said control means for resiliently urging said control means toward the position of abutment with the head of said piston means and thereby effect closure of the aforesaid passage means comprises a coil spring.
 7. The device of claim 1, wherein said means, having a predetermined compression rate, effectively mounted between the end closure means of said hollow pipe means and said control means for resiliently urging said control means toward the position of abutment with the head of said piston means and thereby effect closure of the aforesaid passage means comprises: a coil spring; and means connected to the end closure means of said hollow pipe means for effectively restraining the movement of that end of said coil spring which is opposite said control means.
 8. The device of claim 1, wherein said hydraulic fluid means disposed so as to partially fill said cylindrical chamber to a predetermined level and completely fill said piston chamber, the ports extending through the head of said piston means, and the space between the head of said piston means and the aforesaid first wall of said cylinder means comprises a liquid having a predetermined viscosity.
 9. The device of claim 1, wherein said means connected to said cylinder means and disposed in slidable contact with the external surface of the housing of said piston means for effecting a hydraulic seal therebetween when said piston means is telescopically disposed therein comprises a packing gland.
 10. The invention of claim 1 further characterized by a pair of fittings attached to said cylinder means in such manner as to provide means for supplying compressed air and hydraulic fluid thereto, respectively.
 11. The device of claim 1, wherein said means connected to the other end of said hollow pipe means for effecting the closure thereof comprises: a plurality of threads located around the outside of that end of said hollow pipe means to be closed; and a cap, having internal threads that are compatible with the aforesaid plurality of threads, screwed on the end of said hollow pipe means.
 12. The invention of claim 11, further characterized by means disposed between said hollow pipe means and said cap for effecting a fluid seal therebetween.
 13. The invention of claim 1, further characterized by means connected between said hollow pipe means and said control means for limiting the rotation of said control means a predetermined amount with respect to said hollow pipe means.
 14. The device of claim 13, wherein said means connected between said hollow pipe means and said control means for limiting the rotation of said control means a predetermined amount with respect to said hollow pipe means comprises: a hole located in said control means which extends therethrough in such manner as to provide an open passageway to the external surface of said hollow pipe means; a groove located in the outer surface of said hollow pipe means, said groove being elongated in the direction of travel of said control means, and located in Contiguous disposition with the aforesaid hole for the entire length thereof; and a pin removably press fitted within said hole in such manner as to cause the inner end thereof to slidably fit in said groove and be travel limited thereby.
 15. The device of claim 13, wherein said means connected between said hollow pipe means and said control means for limiting the rotation of said control means a predetermined amount with respect to said hollow pipe means comprises: at least one groove, elongated in the direction of travel of said control means, located in the inner surface of said hollow pipe means; and means connected to said control means extending into said groove in such manner as to provide a slidable fit and a rotational limitation therebetween.
 16. The device of claim 15, wherein said means connected to said control means and extending into said groove in such manner as to provide a slidable fit and a rotational limitation therebetween comprises a keeper pin. 